Up to now, arylpiperazine compounds were proven to be effective to a variety of indications in the field of central nervous system. In particular, U.S. Pat. No. 3,002,976 reported that the following thiophene-engrafted arylpiperazine compound has a pharmacological effect to treat depression. In this formula, R represents hydrogen, methyl group or halogen.

Also, it has been known that effects of buspirone and its structurally related compounds on the treatment of anxiety is due to their selective activities in serotonin (5-hydroxytryptamine: 5HT) sub-type receptor represented by a receptor 5-HT1A. In particular, U.S. Pat. No. 4,988,814 discloses piperazine derivatives showing affinity to the 5-HT1A receptor characterized as therapeutic agents to treat depression and anxiety.

wherein, R1 is alkyl having carbon atoms of 1 to 6; R2 and R3 are each independently alkyl having carbon atoms of 1 to 6, or R2 and R3 are taken together to form polymethylene having carbon atoms of 2 to 12 or to form a 5-norbornen-2-yl residue with carbon atoms bound to the radicals R2 and R3; X is selected from the group consisting of —CO2—, —OCO—, —OCO2—, —N(R7)CO—, —NHNHCO—, —ON(R7)CO—, —CON(R7)—, —N(R7)CO2—, —OCON(R7)— and —N(R7)CON(R8) (wherein, R7 and R8 are each independently is selected from the group consisting of hydrogen; alkyl having carbon atoms of 1 to 6; phenyl; benzyl; and phenyl or benzyl substituted by halo, alkyl having carbon atoms of 1 to 6, alkoxy having carbon atoms of 1 to 6, cyano, nitro or perhalomethyl); R4 is hydrogen or alkyl having carbon atoms of 1 to 6; R5 is selected from the group consisting of hydrogen; alkyl having carbon atoms of 1 to 8; hydroxyalkyl having carbon atoms of 1 to 3; phenyl; benzyl; and phenyl or benzyl substituted by hydroxy, halo, alkyl having carbon atoms of 1 to 6, alkoxy having carbon atoms of 1 to 6, trifluoromethyl, nitro, cyano, carbalkoxy having carbon atoms of 2 to 7, carboxamido, amino, alkylamino having carbon atoms of 1 to 6 or dialkylamino having carbon atoms of 2 to 12; R6 is phenyl, benzyl, 2-, 3- or 4-pyridinyl, 2-pyrimidinyl or 2-pyrazinyl that may be substituted by at least one substituents selected from the group consisting of hydroxy, halo, alkyl having carbon atoms of 1 to 6, alkoxy having carbon atoms of 1 to 6, trifluoromethyl, nitro, cyano, carbalkoxy having carbon atoms of 2 to 7, carboxamido, amino, alkylamino having carbon atoms of 1 to 6, and dialkylamino having carbon atoms of 2 to 12; n is one integer selected from the group consisting of 0, 1, 2, 3, 4 and 5, provided that R6 is not 2-pyrimidinyl when X is —CON(R7)— (wherein, R7 is alkyl), and R6 is not 3,5-di(trifluoromethyl)phenyl when X is CO2, R1, R2 and R3 are methyl and n is 1.
The present inventors have confirmed that an arylpiperazine structure is correlated with an effect to treat pains as well as anxiety and depression, conducted comprehensive researches on the arylpiperazine structure, and found that novel carbamoyloxy arylalkanoyl arylpiperazine compounds have a medical effect in various pain-induced animal models. In particular, the present inventors have found that the novel carbamoyloxy arylalkanoyl arylpiperazine compounds show their therpeutic effects to treat a wide scope of pains including acute pain, chronic pain, neuropathic pain, post-surgery neuropathic pain, diabetic pain, postherpetic neuralgia, inflammatory pain, joint pain, migraine headache and the like, anxiety and depression. Therefore, the present invention was completed on the basis of the above-mentioned facts.